Plug the BNC test lead into Channel A on the PicoScope. Place a black clip onto the black probe (negative) and connect this to a suitable ground point. Connect an Back-pinning Probe to the coloured lead (positive) in order to backpin the connector at the quantity control valve, as illustrated in Figure 1. If a suitable automotive break out lead is available, this may be used instead of the back pinning method.
The valve will have two electrical connections: an ignition positive (15 V) and a switched earth.
The Common-rail Diesel Injection (CDi) quantity control valve is an actuator. It is commonly supplied with an ignition live (15 V) and a duty cycled ground, provided by the CDi control unit, that controls the valve.
The quantity control valve (also referred to as an inlet metering valve or flow regulator) is designed to control the quantity of diesel fuel flowing from the low pressure or lift pump to the pistons of the high pressure pump.
Greater amounts of fuel allowed to the pistons of the high pressure pump result in a higher pressure generated and thus higher pressure in the common rail. Smaller amounts of fuel allowed to the pistons of the high pressure pump result in lower pressure generated and thus create lower pressure in the common rail.
Controlling the quantity of fuel supplied to the high-pressure pump pistons results in lower fuel temperature (often eliminating the need for a fuel cooler) and reduces the load on the high-pressure pump.
Should you suspect a fault with the signal, test the wiring from the CDi control unit to the quantity control valve.
Ensure that the CDi control unit has good power supplies and grounds where required or specified.
This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.
If you have any suggestions to improve this guided test please do so using the 'add comment' button.